<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 闰年能被4整除，并且不能被100整除，或者能被400整除
        var year = prompt('请输入要检测的年份');
        if (year % 4 === 0 && (year % 100 !== 0 || year % 400 === 0)) {
            alert (`${year}是闰年`);
        } else {
            alert (`${year}是平年`);
        }
    </script>
</body>
</html>